The ionic conductivity and the conjugate chemical diffusion of cations and electron holes in Li x Cu 2-x S (0 ≤ x ≤ 0.25) compositions are studied in the temperature range 623 -467 K. In accordance with prediction of the known "mixed mobile ions effect" the partial substitution of copper by lithium in copper sulfide leads to decreasing of the ionic conductivity and it is linked to an increase of activation energy of the ionic conductivity. In comparison with pure copper sulfide the chemical diffusion coefficients in the lithium-contained compounds are smaller too. The observed values of the activation energy of the chemical diffusion are close to those of the activation energy of the ionic conductivity.